1. Field of the Invention
The present invention relates to the field of inductive devices, and more particularly to wire core inductive devices such as transformers, chokes, coils, ballasts, and the like.
2. Description of Related Art
It is common for low frequency application transformers and other inductive devices to be made up of a magnetic core comprising a plurality of sheets of steel, the sheets being die cut and stacked to create a desired thickness of the core. For many years the thickness (thus number of necessary pieces) of the stampings has been determined by a strict set of constraints, e.g. magnitude of eddy currents versus number of necessary pieces. The individual sheets of selected thickness are generally oxide-coated, varnished or otherwise electrically insulated from one another in order to reduce/minimize eddy currents in the magnetic core.
The present inventor has developed wire core inductive devices such as transformers, chokes, coils, ballasts, and the like having a magnetic core including a portion of a plurality of wires rather than the conventional sheets of steel. These devices and related methods of manufacturing the devices are set forth in detail in U.S. Pat. Nos. 6,239,681 and 6,268,786, which are incorporated herein by reference. These devices and methods overcome deficiencies of conventional inductive devices. One particular aspect of the devices, according to the above patents, is the use of different diameter wires for the magnetic core. The wires are arranged to provide a more dense packing of the magnetic core in order to improve its magnetic characteristics. Despite the improved density and magnetic characteristics provided by wires of different diameters, resultant spaces between adjacent wires still limit the overall efficiency of the magnetic core.